PPAPI: Remove threading options; it's always on

This also re-enables thread checking for the host side resource and var trackers. Before, checking was disabled everywhere.

BUG=159240,92909


Committed: r186925
Reverted: r186939 due to build errors

Committed: r187340

Committed: r187427
Reverted: r187668 due to a failing check in Canary, which was fixed here: r187681

Committed: r189518
Reverted: r189682, due to regression in Kraken (see crbug.com/222741)

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=191420
Reverted: r191441, due to new failing PDFResource unit test.

Review URL: https://chromiumcodereview.appspot.com/12378050

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@191510 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ppapi/ppapi_proxy.gypi b/ppapi/ppapi_proxy.gypi
index 8adefd4b..560e510 100644
--- a/ppapi/ppapi_proxy.gypi
+++ b/ppapi/ppapi_proxy.gypi
@@ -71,6 +71,7 @@
           'proxy/interface_list.h',
           'proxy/interface_proxy.cc',
           'proxy/interface_proxy.h',
+          'proxy/locking_resource_releaser.h',
           'proxy/pdf_resource.cc',
           'proxy/pdf_resource.h',
           'proxy/plugin_array_buffer_var.cc',